This invention relates to mining site reclamation and more particularly concerns a method and apparatus for remotely placing explosive charges in mining voids such as auger holes preparatory to detonation for reclamation purposes.
Recent developments in blasting technology have provided the mining and similar industries with techniques for highwall demolition and spoil creation. The techniques use directional and nondirectional charges placed in voids created by mining which are substantially horizontally disposed. The voids can have various and cross-sectional outlines, for example the cross-sectional geometry can be circular, rectangular or oval depending on the mining method creating the void. The voids commence at an entry proximate the cropping of an ore vein and continue inwardly to the depth at which the mining operation ceased. Certain reclamation techniques require the placement of armed individual charges at specific locations in the voids such as auger holes and drift mine shafts. Placement of the charges at specific locations enhances the efficiency of the blast and reduces the cost of demolition and reclamation.
Statuary limitations prevent the entry of personnel into certain classes of voids such as auger holes. Additionally, auger holes, and other types of voids, though substantially horizontal, can slope downward from the entry and may be flooded. This would prevent access by personnel to the void depths for purposes of placing charges for safety reasons.
In certain embodiments of demolition techniques each void is loaded with a plurality of charges. To reduce seismic impact and maximize efficiency the charges to be detonated are fired at specific delayed time intervals. These delays may be only a few hundred nanoseconds. An effective method of producing such small delays is to sequentially attach the charges by means of a detonator cord branch line to a detonator cord trunk line. To insure the positive ignition of the branches of the detonating trunk line, a positive contact cord-to-cord would normally be employed. Contact would be insured by knotting the cords securely or by some similar technique. This form of attachment would however make remote placement difficult.